Closes PerryTS#226. Pre-fix every `fs.appendFileSync(path, content)` wrote 0 bytes — the file wasn't even created on a fresh path. The runtime function (`crates/perry-runtime/src/fs.rs::js_fs_append_file_sync`) was already correct (`OpenOptions::new().create(true).append(true).write_all(...)`), the gap was in two earlier passes. The HIR carries a dedicated `Expr::FsAppendFileSync(path, content)` variant for this. The named-import path of the SWC→HIR lowerer already produced it (`import { appendFileSync } from "fs"`), and the JS / WASM backends both had codegen arms for it. Two things on the LLVM track were missing: 1. `crates/perry-hir/src/lower/expr_call.rs` — the namespace-import path (`import * as fs from "fs"; fs.appendFileSync(...)`) had arms for `writeFileSync` / `existsSync` / `mkdirSync` / `unlinkSync` etc. but not `appendFileSync`. Without this, the call slipped past as a generic `Call { callee: PropertyGet { object: NativeModuleRef("fs"), property: "appendFileSync" }, args: [...] }` and `Expr::FsAppendFileSync` never got emitted for the most common usage shape. Added the arm next to `writeFileSync`. 2. `crates/perry-codegen/src/expr.rs` — even when the HIR variant was emitted (named-import path), the LLVM backend had no arm next to `Expr::FsWriteFileSync`. The call fell through and was silently dropped. Added the arm; same shape as `FsWriteFileSync`, calls `js_fs_append_file_sync`. Plus the runtime declaration in `crates/perry-codegen/src/runtime_decls.rs` so the LLVM module declares `js_fs_append_file_sync` for the linker. # Verified `cargo build --release -p perry` clean, `cargo test -p perry-hir -p perry-codegen --lib` green (20 tests, no regressions). End-to-end against `node --experimental-strip-types` on the new `test-files/test_fs_appendfile.ts`: perry: node: line one line one <blank> line one line one line two line two <blank> line one line one line two line two line three line three Identical output. # Issue diagnosis correction The issue body diagnosed only the codegen-arm-faltante (path 2 above). While iterating on this fix I hit the surprising case where adding just that arm changed nothing for `import * as fs from "fs"; fs.append(...)`. Tracing the HIR confirmed the namespace-import path needed extending too. Both arms in this commit; either alone is insufficient for the common usage pattern.

Commits

Commits on Apr 28, 2026

fix(fs): wire fs.appendFileSync end-to-end